# Ultraviolet light of wavelength 280 nm is used in an experiment on photoelectric effect with lithium ( = 2.5 eV) cathode. Find(a) the maximum kinetic energy of the photoelectrons and(b) the stopping potential.

Arun
25758 Points
4 years ago
(a) K.E. = (hc / $\lambda$)  – $\phi$0
= (1242 ev-nm/ 280 nm) – 2.5 ev
= 1.9 ev
(b) stopping potential is given by
ev = K.E.max
V = 1.9 ev / e
= 1.9 Volt